[Bug bootstrap/51705] FreeBSD uses unsupported C++11 features when __cplusplus == 201103L

["sgk at troutmask dot apl.washington.edu" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51705

--- Comment #16 from Steve Kargl <sgk at troutmask dot apl.washington.edu> 2011-12-30 04:01:52 UTC ---
On Thu, Dec 29, 2011 at 11:12:39PM +0000, redi at gcc dot gnu.org wrote:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51705
> 
> --- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-12-29 23:12:39 UTC ---
> (In reply to comment #10)
> > I have no qualms with this.  If it does not support C++03, then
> > should advertise that it does.
> 
> (Assuming you meant should *not*) that's not very useful in practice.  If no
> headers anywhere in existence actually use 'export' then do you seriously argue
> that no compiler should ever define __cplusplus == 199711L?

Yes, I meant 'not'.

Yes, if 'export' is not support, then __cplusplus should not be defined 
to indicate that g++ supports that standard.

I have no problem with -std=c++11 enabling C++11 features and evening
trying to apply a strict interpretation of C++11.  But, if g++ does
not support the entire language at 201103L, then it should not advertise
that it does.  

> > If this is the case, then it definitely should not advertise
> > that it does support C++11.
> 
> But pragmatically, it helps more users to do the Right Thing for what users use
> and want.  Clearly we have a real problem here for FreeBSD, and should be fixed
> by not defining __cplusplus==201103L or via fixincludes, but I maintain it was
> pretty silly to update headers to use bleeding edge features before checking if
> they work with bleeding edge compilers.  Yes, GCC 4.7 might be bleeding edge,
> but so is [[noreturn]] support so not checking it works before using it is just
> sloppy.

Given the area FreeBSD that Ed works on, I suspect it is supported by
at least one compiler.  

> (In reply to comment #11)
> > But this has nothing to do with FreeBSD specifically. It will apply to
> > basically any operating system in the future.
> > 
> > Say, GCC 4.8 (late 2012?) will support [[noreturn]] properly and some OS vendor
> > decides to start using it by the year 2016 in its header files. That will still
> > prevent you from compiling GCC 4.7 then, in case some piece of software depends
> > on it.
> 
> *ahem* It will prevent you using 4.7.0 20111229 (experimental) - this problem
> doesn't exist with any released version. We can get it fixed (FreeBSD is a
> primary platform after all, so this should be P2 or even P1) if we identify the
> problem correctly.  I believe the right fix is fixincludes.  Feel free to keep
> arguing otherwise, but wherever the problem lies, it's not that libstdc++ uses
> C++11 features (note that libstdc++ only ever checks __GXX_EXPERIMENTAL_CXX0X__
> so is agnostic about the value of __cplusplus)

Well, the correct fix is for g++ not to define __cplusplus as 201103L.
Or, the correct fix is for the g++ developers to implement [[noreturn]].
But, common sense, here a hack to make it work on FreeBSD.

2011-12-29  Steven G. Kargl  <kargl@gcc.gnu.org>

    * inclhack.def:  Disgusting hack to workaround brain damage of
    defining __cplusplus as 201103L with -std=c++11 when g++ does
    not support c++11.
    * fixincl.x: regenerated.
    * genfixes: Fix a version test.

Index: inclhack.def
===================================================================
--- inclhack.def    (revision 182738)
+++ inclhack.def    (working copy)
@@ -20,6 +20,21 @@ autogen definitions fixincl;
 FIXINC_DEBUG = yes;
 #endif

+/*
+ * g++ -std=c++11 defines __cplusplus to 201103L, which lies about
+ * the level of support g++ has for the C++11 standard.
+ */
+fix = {
+    hackname  = cdef_cplusplus;
+    mach      = "*-*-freebsd10.*";
+    files     = sys/cdefs.h;
+    select    = "\\\\[\\\\[noreturn\\\\]\\\\]";
+    sed       = "s/\\\\[\\\\[noreturn\\\\]\\\\]/__dead2/";
+    test_text = "#include <sys/cdefs.h>";
+};
+
+
+
 /* On AIX when _LARGE_FILES is defined stdio.h defines fopen to
  * fopen64 etc. and this causes problems when building with g++
  * because cstdio udefs everything from stdio.h, leaving us with
Index: fixincl.x
===================================================================
--- fixincl.x    (revision 182738)
+++ fixincl.x    (working copy)
@@ -2,11 +2,11 @@
  * 
  * DO NOT EDIT THIS FILE   (fixincl.x)
  * 
- * It has been AutoGen-ed  November  7, 2011 at 01:16:39 PM by AutoGen 5.10
+ * It has been AutoGen-ed  December 29, 2011 at 06:29:22 PM by AutoGen 5.12
  * From the definitions    inclhack.def
  * and the template file   fixincl
  */
-/* DO NOT SVN-MERGE THIS FILE, EITHER Mon Nov  7 13:16:39 EST 2011
+/* DO NOT SVN-MERGE THIS FILE, EITHER Thu Dec 29 18:29:22 PST 2011
  *
  * You must regenerate it.  Use the ./genfixes script.
  *
@@ -15,7 +15,7 @@
  * certain ANSI-incompatible system header files which are fixed to work
  * correctly with ANSI C and placed in a directory that GNU C will search.
  *
- * This file contains 222 fixup descriptions.
+ * This file contains 223 fixup descriptions.
  *
  * See README for more information.
  *
@@ -43,6 +43,42 @@ static char const sed_cmd_z[] = SED_PROG

 /* * * * * * * * * * * * * * * * * * * * * * * * * *
  *
+ *  Description of Cdef_Cplusplus fix
+ */
+tSCC zCdef_CplusplusName[] =
+     "cdef_cplusplus";
+
+/*
+ *  File name selection pattern
+ */
+tSCC zCdef_CplusplusList[] =
+  "sys/cdefs.h\0";
+/*
+ *  Machine/OS name selection pattern
+ */
+tSCC* apzCdef_CplusplusMachs[] = {
+        "*-*-freebsd10.*",
+        (const char*)NULL };
+
+/*
+ *  content selection pattern - do fix if pattern found
+ */
+tSCC zCdef_CplusplusSelect0[] =
+       "\\\\[\\\\[noreturn\\\\]\\\\]";
+
+#define    CDEF_CPLUSPLUS_TEST_CT  1
+static tTestDesc aCdef_CplusplusTests[] = {
+  { TT_EGREP,    zCdef_CplusplusSelect0, (regex_t*)NULL }, };
+
+/*
+ *  Fix Command Arguments for Cdef_Cplusplus
+ */
+static const char* apzCdef_CplusplusPatch[] = { sed_cmd_z,
+    "-e", "s/\\\\[\\\\[noreturn\\\\]\\\\]/__dead2/",
+    (char*)NULL };
+
+/* * * * * * * * * * * * * * * * * * * * * * * * * *
+ *
  *  Description of Aab_Aix_Stdio fix
  */
 tSCC zAab_Aix_StdioName[] =
@@ -9034,14 +9070,15 @@ static const char* apzX11_SprintfPatch[]
  *
  *  List of all fixes
  */
-#define REGEX_COUNT          264
+#define REGEX_COUNT          265
 #define MACH_LIST_SIZE_LIMIT 181
-#define FIX_COUNT            222
+#define FIX_COUNT            223

 /*
  *  Enumerate the fixes
  */
 typedef enum {
+    CDEF_CPLUSPLUS_FIXIDX,
     AAB_AIX_STDIO_FIXIDX,
     AAB_DARWIN7_9_LONG_DOUBLE_FUNCS_FIXIDX,
     AAB_DARWIN7_9_LONG_DOUBLE_FUNCS_2_FIXIDX,
@@ -9267,6 +9304,11 @@ typedef enum {
 } t_fixinc_idx;

 tFixDesc fixDescList[ FIX_COUNT ] = {
+  {  zCdef_CplusplusName,    zCdef_CplusplusList,
+     apzCdef_CplusplusMachs,
+     CDEF_CPLUSPLUS_TEST_CT, FD_MACH_ONLY,
+     aCdef_CplusplusTests,   apzCdef_CplusplusPatch, 0 },
+
   {  zAab_Aix_StdioName,    zAab_Aix_StdioList,
      apzAab_Aix_StdioMachs,
      AAB_AIX_STDIO_TEST_CT, FD_MACH_ONLY | FD_SUBROUTINE,
Index: genfixes
===================================================================
--- genfixes    (revision 182738)
+++ genfixes    (working copy)
@@ -62,7 +62,7 @@ fi
 AG="autogen $AG"
 set -e

-if [ -z "`${AG} -v | fgrep 'Ver. 5.'`" ]
+if [ -z "`${AG} -v | fgrep '5.'`" ]
 then
   echo "AutoGen appears to be out of date or not correctly installed."
   echo "Please download and install:"